Fix handling of duplicate mentions in incoming status `Update` (#33911)

app/services/activitypub/process_status_update_service.rb

@@ -225,7 +225,7 @@ class ActivityPub::ProcessStatusUpdateService < BaseService
       nil
     end
 
-    @status.mentions.upsert_all(currently_mentioned_account_ids.map { |id| { account_id: id, silent: false } }, unique_by: %w(status_id account_id))
+    @status.mentions.upsert_all(currently_mentioned_account_ids.uniq.map { |id| { account_id: id, silent: false } }, unique_by: %w(status_id account_id))
 
     # If previous mentions are no longer contained in the text, convert them
     # to silent mentions, since withdrawing access from someone who already

spec/lib/activitypub/activity/create_spec.rb

@@ -37,10 +37,16 @@ RSpec.describe ActivityPub::Activity::Create do
         content: '@bob lorem ipsum',
         published: 1.hour.ago.utc.iso8601,
         updated: 1.hour.ago.utc.iso8601,
-        tag: {
+        tag: [
+          {
             type: 'Mention',
             href: ActivityPub::TagManager.instance.uri_for(follower),
           },
+          {
+            type: 'Mention',
+            href: ActivityPub::TagManager.instance.uri_for(follower),
+          },
+        ],
       }
     end
 

spec/services/activitypub/process_status_update_service_spec.rb

@@ -18,6 +18,7 @@ RSpec.describe ActivityPub::ProcessStatusUpdateService do
       tag: [
         { type: 'Hashtag', name: 'hoge' },
         { type: 'Mention', href: ActivityPub::TagManager.instance.uri_for(alice) },
+        { type: 'Mention', href: ActivityPub::TagManager.instance.uri_for(alice) },
         { type: 'Mention', href: bogus_mention },
       ],
     }